<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			div{
				width: 100px;
				height: 100px;
				background-color: blue;
				margin: 2px;/* margin四个方向都设置了外边框 */
				border: 2px solid red;/* border边框,solid类型实线,可以做成点点虚线的样子 */
				padding: 2px;/* 内边框 */
			}
		</style>
	</head>
	<body>
		<div></div>
		<div></div>
		<div></div>
	</body>
</html>